25806509 has 2 divisors, whose sum is σ = 25806510. Its totient is φ = 25806508.

The previous prime is 25806499. The next prime is 25806533. The reversal of 25806509 is 90560852.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 22372900 + 3433609 = 4730^2 + 1853^2 .

It is a cyclic number.

It is not a de Polignac number, because 25806509 - 2¹⁶ = 25740973 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (25806569) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 12903254 + 12903255.

It is an arithmetic number, because the mean of its divisors is an integer number (12903255).

Almost surely, 2^25806509 is an apocalyptic number.

It is an amenable number.

25806509 is a deficient number, since it is larger than the sum of its proper divisors (1).

25806509 is an equidigital number, since it uses as much as digits as its factorization.

25806509 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 21600, while the sum is 35.

The square root of 25806509 is about 5080.0107283351. The cubic root of 25806509 is about 295.5128835249.

The spelling of 25806509 in words is "twenty-five million, eight hundred six thousand, five hundred nine".